I've been consistently having problem receiving email from gmail.com users outside the company domain. If they send attachments, my users can experience up to 3 days of delay before the message is received. I've run several headers analyses on the email once they're received and it seems to always be hung up on google mx servers. I'm never finding a problem in the smtp logs in regards to deferrals or blocks or NDRs. Once google decides to release the email, our smtp firewall receives and delivers almost instantly every time. Any thoughts on this? I've been dealing with this for weeks.